Kara no Kyōkai (空の境界, Kara no Kyōkai? lit. Boundary of Emptiness) is a Japanese novel series, authored by Kinoko Nasu and illustrated by Takashi Takeuchi. It is also known under the name Rakkyo (らっきょ, Rakkyo?), and its tagline The Garden of Sinners.

The series originally begun from October 1998 as a series of five chapters released online on Nasu and Takeuchi's dōjin-based website, Takebōki (竹箒, Takebōki?), with its final two chapters being released at Comiket 56 in August 1999. Nasu and Takeuchi were later to form Type-Moon, and in 2001, featured a portion of the book in its 2001 Tsukihime fandisk, Tsukihime PLUS-DISC, which saw it gain significant popularity, leading it to be released as a dōjinshi publication at Comiket 61 on December 30, 2001.

On September 2002, a drama CD based on the series was released, and on August 6, 2004, noted publisher Kodansha released the series as a commercial publication, which enjoyed immense popularity, with 5000 limited-edition versions of the novel being sold almost immediately upon release. Both editions of Kara no Kyōkai altogether sold more than 500,000 copies. In 2009, Del Rey Manga will begin printing the Kara no Kyōkai novel. This was confirmed in the first volume of Del Rey's Faust release. The series is regarded as being set in the same world as another Type-Moon series, Tsukihime, with the protagonist of the series, Shiki Ryōgi, possessing similar abilities as Tsukihime's protagonist, Shiki Tohno, and another Tsukihime character, Aoko Aozaki's sister, Tōko Aozaki (who was briefly mentioned in Tsukihime), also being featured.

The series is being adapted into an ongoing anime movie series, divided into seven chapters, which are animated by the studio ufotable after being announced. The first chapter, titled Overlooking View (俯瞰風景, Fukan Fūkei?), premiered across Japanese theaters on December 1, 2007, with the second,third, fourth, and fifth chapters, A Study in Murder (Part 1) (殺人考察(前), Satsujin Kōsatsu (Zen)?), Remaining Sense of Pain (痛覚残留, Tsūkaku Zanryū?), Void Shrine (伽藍の洞, Garan no Dō?), and Spiral Paradox (矛盾螺旋, Mujun Rasen?) being released soon after on December 29, 2007, followed by January 26, 2008 May 24, 2008, and August 16, 2008 respectively. In connection with the movie's release, the novels are once again being reprinted, as three volumes with new illustrations.